Di Lecce Silvia, Albrecht Tim, Bresme Fernando
Department of Chemistry, Imperial College London, London, SW7 2AZ, UK.
Phys Chem Chem Phys. 2017 Apr 5;19(14):9575-9583. doi: 10.1039/c7cp01241a.
The application of a thermal gradient to an aqueous electrolyte solution induces the Soret effect, and the salt migrates towards hot (thermophilic) or cold regions (thermophobic). Experimental studies of LiCl reported changes in the sign of the Soret coefficient as well as a minimum in this coefficient at specific salt concentrations and temperatures. At the minimum the thermodiffusive response of the solution is enhanced significantly. We have performed non-equilibrium molecular dynamics simulations of LiCl solutions to quantify the dependence of the sign change and minimum of the Soret coefficient with salt concentration and temperature. We find that the ion mass plays a secondary role in determining the magnitude of the Soret coefficient, while the diameter of the cation has a significant impact on the coefficient and on the observation of the minimum. Our simulations show that the ordering of water around Li plays a key role in determining the Soret coefficient of LiCl salts.
对水性电解质溶液施加热梯度会引发索雷特效应，盐会向热区（嗜热）或冷区（畏热）迁移。对氯化锂的实验研究表明，索雷特系数的符号会发生变化，并且在特定的盐浓度和温度下该系数会出现最小值。在最小值处，溶液的热扩散响应会显著增强。我们对氯化锂溶液进行了非平衡分子动力学模拟，以量化索雷特系数的符号变化和最小值对盐浓度和温度的依赖性。我们发现，离子质量在决定索雷特系数的大小时起次要作用，而阳离子的直径对该系数以及最小值的观测有显著影响。我们的模拟表明，锂周围水的有序排列在决定氯化锂盐的索雷特系数方面起着关键作用。
